Looking back at four decades of satellite remote sensing we can safely say that more research has been conducted into manipulating the spectral information content of images than any other aspect of digital image analysis and great progress has been made. Some techniques, such as those associated with image classification, have undergone continuous improvements throughout, others like canopy reflectance modelling only emerged in the last decade. In order to understand why these developments have occurred we require a better understanding of the nature of information contained in the spectral domain. The first section of this topic introduces methods to identify and enhance the spectral component of image data. The second part concentrates on techniques to extract information.

Before commencing study of this section I would like to draw your attention to one of the conclusions. It is not possible to declare one approach better than another. Their performance is strongly data-dependent and, as with all information products, the quality of the data is ultimately determined by their fitness-for-purpose. One approach may be more useful in one application but it is not possible to generalise this statement to every application. The more experience you can gather the more accomplished you will become.